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Sumitogi


wunderlich

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Hi folks,

 

because I have to polish some softmetalwork recently I tried a traditional japanese charcoal polishing procedure. The result was not mirrorlike, rather matt.

:D

I want to collect information on this subject into this tread. There are information on sword polishing obtainable on different sources but very less for polishing soft metals.

 

The use of toishi (whetstones) is shown Here

 

I found two short Quicktime movies showing a nuri-shi while polishing.

 

The first stage is stone polishing

 

Ishitogi

 

followed by charcoal polishing

 

Sumitogi

 

My question is which kind of charcoal is used best when traditional roiro sumi is not available?

Perhaps some of the members here have some experiences about that.

 

regards

Karl :D

 

Hi Karl,

I use this procedure as part of my living, but I learned it from Ford and I use supplies that he provided me with. So I have not had to purchase any myself... yet. I have two grades of Ho wood Charcoal. One has the more gentle polishing action than the other and they are used in succession. The Final stage is powdered charcoal used with a Migaki brush. It is not just up to the grade of abrasive though. I find that pressure is also important. Working a given pressure with a particular stage followed by a pass with lighter pressure will yield a higher grade finish. I believe that all the charcoal products are available for purchase in Japan. Ford is the one to ask where to get these supplies.

I probably would not have looked for alternatives until I ran out of my current stock. I have the wood specie names though and if you could not find the charcoal you might be able to buy the wood. Making charcoal is simple. I don't know which specie the powdered charcoal is made from, but I would guess it is the softer variety mentioned and the Brush allows it to work with a gentler action for a finer finish.

Honestly I use Graded abrasive powder with a brush as an alternative to the powdered charcoal. The Powdered charcoal that Ford gave me is still pretty scratchy for some reason. That could just be my inexperience though. I do get good results with Silicon carbide powders used the same way. "1,000 mesh size" used with a Migakebaki yields a fairly good final polish. You can keep going finer and finer until you achieve the result you are looking for. I find it difficult to see much improvement beyond 1500 mesh size. You can find these powders through places that sell rock tumbling/polishing supplies.

regards,

Patrick

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Pottery/ceramics supplies too! Glaze materials, silica (flint, silica, quartz is the mantra I learned, all the same) of different mesh, not as varied as rock polishing supplies though. Other powdered minerals at ceramic supplies as well, of certain mesh sizes.

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Aloha Karl,

 

If you are set on trying traditional charcoal powder as an abrasive/polish, perhaps this info will help. As I understand it, Ho wood is related to magnolia (Magnolia grandiflora) and is somewhat available. Magnolia, in turn, is related to yellow or tulip poplar (Liriodendron tulipifera). Do not confuse this with true white poplar (Poplar spp.) like aspen. Anyway, I do not know if A=B=C means A=C, but one of those should produce a lightweight, homebrew charcoal. Descriptions point out mineral streaks (dark patches), so you might want to avoid those areas when setting up your burn.

 

KC

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Hallo Patrick and Karl,

 

thanks for the hints. Today I tried a commercial sold soft willow charcoal (for drawing purposes). This worked great. For still finer abrasion I ground hard barbecue charcoal in a mortar very fine. This powder was rubbed on with my thumb.

Ok, it isnt a mirror finish yet.... :blush:

 

I made a kind of test plate. I will check out if it is possible to make a suiteable foto of it. If so, I will post it later.

 

regards

Karl

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Is the powder something that could be sifted through a very fine glaze sieve? One could put the powder into water to prevent the fine powders from escaping and being inhaled. Here is an example. It has been a long time, so I don't remember how fine the brass screens can be, but the screens or sieves at the pottery supplier can be orderer a very fine mesh count. I used them in the pottery studio, to mix glazes and colorants.

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Aloha Karl,

 

That was a very smart move using the drawing charcoal as a starting point. :blush: In the case of pulverizing from chunk, try using two flat steel plates after initial mortar/pestle treatment. Sift the coarse grind, then powderize between the plates in a swirling motion.

 

KC

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Hi,

 

here is my Togi-Test-Plate. :blush:

I beg your pardon but the plate was made fast. It was done just to figure out the behaviour of my material. All stones and the charcoal were used with water. The powder was applied with the thumb. The scraper was used in two directions the other stuff was moved circular across the metal. Of course a migaki-hake is more appropriate when polishing around or within a relief.

 

 

 

I hope you can see something on the pic. :blink:

 

regards

Karl :)

 

edit.: The plate was fotographed from two directions to handle the light somewhat...

 

 

 

 

 

the actuall size of the sheet is 17cm length. Is not really easy to make a good pic of it. <_<

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I know Ford is lurking around again, so I expect he will pipe in with some valuable input when he gets more settled in.

You might find linear strokes more effective than circular. Each time a finer stone is used you scrub the metal from a different direction. This gives you accurate feed back on your progress of scratch removal and insures and even pass on the surface. Circular strokes hide scratches from the previous grit and create more work. I use linear strokes with all the solid abrasives right up through the solid charcoals. I have found the brush is not just used in hard to reach places it is actually a key element in getting the surfaces up to a high gloss including broad flat areas. I find that using my fingers rather than the brush make the abrasive behave more aggressive and results in a lower quality finish. Plus I don't like to turn my fingers black :blush: . Using the same abrasive with the brush results in a better final polish. The action of the particles being pushed/rolled along rather than ground in with your finger is finer. As you pointed out the brush is also useful when working around details.

Patrick

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Great test plate idea Karl W! I suggest that you break the rule and post a photo that is longer than 640, just of the plate and test areas. Add that to the post that has the whole photo, so we will know what it is related to. It would be interesting to see more detail this time.

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  • 2 weeks later...

Use only charcoal from leafy trees. Very good effect gives Japanese oak. I use old bokken that I have broken.

Nice effect gives when you take some charcoal, and pur boiling water on it, leave it for some time and use substance that gather on surface. It clean any fat very nice. And good diamond powder is also great. (it is charcoal too after all ;) )

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